1. Technical Field
The present invention relates to a fluid injection device in which the characteristic of fluid to be injected can be easily set to a desired state in accordance with various situations.
2. Related Art
With respect to a surgery based on injected fluid, the substance of an internal organ can be incised while preserving vasculature such as blood vessels, and also incidental damage applied to living tissues other than the incised site is minor. Therefore, the load imposed on a patient is small. Furthermore, bleeding is little, so that bleeding does not disturb the field of vision of an operational field and thus a rapid operation (surgery) can be performed. Therefore, this operation is frequently clinically applied particularly to hepatic resection, etc. in which bleeding from small blood vessels gives a lot of trouble (for example, JP-A-63-99853).
In the technique as disclosed in the above publication, a pump as a pressurizing source of liquid (fluid) is provided at the outside, and high-pressure fluid is led through a flexible tube to a treatment site. Therefore, even when pressure pulsation is generated by the pressurizing source, injection of the fluid causes continuum flow because the tube has elasticity. When the injection of fluid is pulsated flow, the incision (exsection) performance is enhanced by impact of bow wave. However, when the injection of fluid is continuum flow, the incision performance of living tissues is insufficient, and also the flow amount to be injected is large. Therefore, droplets of living tissues, etc. from the incision (exsection) site easily fly and these droplets may introduce an infection to an operator.
As an improvement proposal of the fluid injection device as described above is known a method of generating fluid jet by which means for making fluid flow is provided in a fluid chamber and vapor bubbles of fluid is intermittently generated by heating means in the fluid chamber so that the internal pressure in the fluid chamber is intermittently increased and pulsated fluid is injected at high speed (For example, JP-T-2003-500098).
Furthermore, a fluid injection device disclosed in JP-A-2005-152127 which has been filed by the inventors of this application can inject pulsated fluid at high speed and high repetitive frequency, and the control thereof is easy. Furthermore, the injection of the pulsated fluid enhances the incision performance of tissues in the operation, etc., and also makes it possible to reduce the fluid amount, so that the fluid is little trapped in the operational field. Accordingly, this method has an effect of enhancing visibility and preventing scattering of the tissues.
Only the generated pressure of the pump as the pressurizing source can be set as a control parameter in JP-A-63-99853, however, various control parameters can be set in the methods of disclosed in JP-T-2003-500098 and JP-A-2005-152127. In JP-A-2005-152127, the wave height value of pulsation, the frequency of pulsation, the pulsation number constituting a fluid stream (group), the interval between fluid streams (groups), etc. can be set as the control parameters. By setting these values properly, it is possible to properly exsect soft tissues of a living body whose hardness and structure vary every place.
For example, by increasing the wave height of pulsation, a harder tissue can be exsected. However, in the case of the same tissue, incision of the tissue concerned progresses more deeply (i.e., a deeper tissue can be also incised) by injecting the fluid for the same time. At this time, when a surgeon wants to make the exsection progress depth equal to that before the adjustment, the adjustment can be performed by reducing the pulsation number constituting the fluid stream or increasing the time interval between the fluid streams to reduce the injected fluid amount.
Furthermore, when an fluid infusion bag or the like is used to supply fluid to a fluid injection portion by using force of gravitation, the amount of fluid to be supplied is limited by the fluid resistance of a fluid channel. At this time, if the control parameters are set so that the injection amount of fluid exceeds the limit of the supplied fluid amount, the injection state of the fluid is unstable, and the exsection performance may be reduced.
However, it is very difficult that these plural control parameters which are mutually correlated with one another are properly adjusted by an surgeon or an operator under the supervision of the surgeon during a time-limited operation. Furthermore, in a fluid injection device in which the supplied fluid amount is limited by the structure thereof, even when a surgeon wants to incise a tissue more deeply and thus increase the pulsation number constituting the fluid stream, there is a case where no desired characteristic is obtained or the operation is unstable because the supplied fluid amount is limited.